Recipe Tips

Preparation

Boil juice in heavy large pot until reduced to 1 cup, about 30 minutes. Add pears and pinch of salt; return to boil. Reduce heat, cover, and simmer until pears are very soft, stirring occasionally to immerse pears in juice, about 25 minutes.

Transfer mixture to processor and puree until smooth. Return puree to same pot. Scrape in seeds from vanilla bean; add bean. Cover partially; simmer over medium-low heat until puree is thick enough to mound slightly on spoon, stirring often and being careful when removing lid (puree will spatter vigorously), about 10 minutes. Remove from heat. Discard vanilla bean. Stir in rosemary and vinegar. Cover; let stand 30 minutes to infuse. Discard rosemary. Cool to room temperature. Cover and chill until cold, about 4 hours. DO AHEAD: Can be prepared 2 weeks ahead. Keep chilled.